The problem is asking for us to solve for the circumference. However, the only provided information is the circle's diameter. In this kind of a problem, it's important think about how the provided information may relate to the information we need in order to solve for the problem. 

The circumference of a circle is determined by the formula:  where r is radius. It can also be written as   because the diameter is twice the length of the radius. 

We can now easily see that the two concepts, diameter and circumference, are related. Therefore, we just need to substitute the diameter value into the circumference formula to solve. 

The problem is asking for us to solve for the circumference. However, the only provided information is the circle's diameter. In this kind of a problem, it's important think about how the provided information may relate to the information we need in order to solve for the problem. 

The circumference of a circle is determined by the formula:  where r is radius.

We can now easily see that the two concepts, radius and circumference, are related. Therefore, we just need to substitute the radius value into the circumference formula to solve. 

You and your friends are ordering pizza for your Friday night Mathathon. You decide to order three pizzas, each 16" in diameter. Find the circumference of each pizza to the nearest tenth.

We are asked to find the circumference of a circle. Don't get too hungry!

We can find the circumference using the following formula:

Now, we know that 2r=d, so our formula becomes:

Simply plug in our diameter and solve for C!

So our answer is 50.3 in

Start by noticing that in the given figure, the diameter of the circle is the same as the length of a side of the square.

Use the area to find the length of a side of a square.

Next, use this to find the circumference of a circle. Recall how to find the circumference of a circle:

Find the circumference of a circle given that the distance from its center to its edge is 6.25 meters.

Find the circumference via the following:

Now, we have our radius, but the wording is a funny way of putting it. The distance from the center to any point on the edge is the same thing as a radius.

Plug in and chug to get our answer.

So, our answer is 36.27 m

First we need to recognize that we are given the length of the radius which is 21 cm. We need to know that the diameter of a circle is twice the length of the radius, so our diameter is 42cm.

Now we need to recall the formula for circumference of a circle:

Where  is diameter.

We can plug in 42cm for our diameter and use 3.14 for pie

Then we multiply

Notice our answer remains in centimeters

The radius of the swimming pool is half the diameter, or 25 feet. 

The area of the swimming pool is  times the square of the radius, or

 square feet, or 

 square yards. 

The manager will need to buy a number of square yards of tarp equal to the next highest multiple of ten, which is 220 square yards.

The radius of the swimming pool is half the diameter, or 15 meters. 

The area of the swimming pool is  times the square of the radius, or

 square meters. 

The manager will need to buy a number of square yards of tarp equal to the next highest multiple of ten, which is 710 square meters.

The diameter of the circle - the distance from one point to the opposite point - is 10 units, so the circumference is this multiplied by , or .

Be careful on several counts for this question.  First, remember that you need the radius for calculating area.  Therefore, since you know that the diameter is , you can say that the radius is .

Next, be very careful given that there is already a  in your radius.  The formula for the area of a circle is:

For your data, this is: